If memory serves, what we in the US now call biscuits, crackers, and cookies were all called biscuits. So both left and right-pondian usages were part of the original definition. My grandparents, born at the end of the 19th century, still usually called crackers biscuits into the 1970s although youngsters like me were confused. The now defunct Uneeda Biscuit, made by the National Biscuit Company/Nabisco, was always a staple in her pantry and the product survived into the 21st century. Perhaps someone with OED access can pin down some actual dates for the divergence of usage and the and when cookie and cracker took over left of the pond.